1. Field of the Invention
Embodiments of the invention include polymeric compounds, and compositions including such compounds, that may be used in forming barrier coating layers for protecting underlying photoresist compositions and methods of utilizing such compounds and compositions. For example, compounds and compositions according to example embodiments of the invention may be used in manufacturing semiconductor integrated circuits, particularly with respect to methods for forming photoresist layers and patterns having a barrier coating layer that will improve the performance of the photoresist in, for example, immersion photolithography.
2. Description of the Related Art
In fabrication processes for manufacturing semiconductor devices, photolithographic processes are used repeatedly to form a wide variety of patterns. The smallest lines and spaces that can be formed using a particular photolithographic process are limited, to some degree, by the wavelength of the light used to expose the pattern. For example, line patterns on the order of about 60 nm represent a lower limit to the patterns that can be produced using a conventional ArF laser (193 nm) light source.
Immersion photolithography processes have been suggested as alternatives to the conventional lithographic processes that can overcome the wavelength limitations associated with the conventional use of ArF laser light sources. In immersion photolithography processes, the gap or space formed between a lens and the wafer surface is filled with liquid that enhances the system performance.
In photolithography processes, the numeral aperture (NA) of an exposure system can be calculated from the equation:NA=n Sin(a)in which n is the refractive index (RI) of an immersion medium and α is the angle between the optical axis of the system and light entering an object lens farthest from the optical axis. In general, a larger NA and/or a light source having a shorter wavelength will tend to improve the resolution that can be obtained by the imaging system. Because the immersion medium used in immersion photolithography tends to increase the NA to a value greater than 1, for example, achieving NA values greater than or equal to 1.3, the resolution of is increased. In particular, when H2O is used as the immersion medium, improved resolution and improved depth of focus (DOF) can be achieved when compared with a conventional “dry” photolithographic process using can be attained because the refractive index, n, of water is 1.44.
However, using H2O as an immersion liquid can lead to several problems including, for example, the tendency of photoresist components such as photoacid generators (PAG) and/or bases to leach into water from the photoresist, thereby compromising the performance of the photoresist and/or contaminating the lens. One method for addressing this problem involves forming a barrier coating layer on the photoresist as disclosed in, for example, by R. R. Dammel et al. in J. Photopol. Sci. Tech., 587, 4 (2004), the disclosure of which is hereby incorporated, in its entirety, by reference. The top coating or barrier coating layer prevents or reduces contact and transfer between the immersion medium and the photoresist, thus preventing or reducing the likelihood that one or more of the photoresist components will be leached from the photoresist layer.
Barrier coating compositions for use in immersion photolithography processes should exhibit relatively low solubility in the immersion medium for at least the duration of the exposure process, exhibit relatively low absorbance at the wavelength of the exposure light source, exhibit relatively good solubility in a developing solution after being exposed, and should exhibit no more than minor intermixing with the photoresist layer to which it is applied.